The molecular mechanisms for, the cardioprotective effects of low doses of ethyl alcohol remain uncertain while the health related benefits gain support from studies with human subjects. The compromised coronary vasculature in patients with cardiovascular disease leads to intermittent ischemia-reperfusion cycles. Alcohol protects against cardiac ischemic damage through a pre-conditioning mechanism involving the ATP catabolite, adenosine and nitric oxide (NO) derived from INOS. The long term cardioprotective effects, associated with ischemic pre-conditioning cannot be induced in the INOS knock out mouse. Accordingly, this model will be used to test the role of INOS in cardioprotection induced by chronic low dose alcohol intake. Herein, the novel concept is introduced that enhanced NO production induced by low dose alcohol protects the heart from ischemic damage on reperfusion through its modulatory effects on mitochondrial respiration and calcium. It is based upon previous studies and preliminary data that show 1) a major component of myocardial-reperfusion damage is due to mitochondrial dysfunction on reperfusion 2) NO inhibits reperfusion damage 3) NO prevents calcium uptake by mitochondria while inhibiting respiration 4) ischemic pre-conditioning involves INOS formation in the heart. A key and vital difference between mitochondrial blockade through oxygen deprivation and NO exposure is that mitochondrial NO inhibition does not lead to calcium accumulation. These data have led to the hypothesis that a critical mechanism contributing to low dose alcohol cardioprotection is through an NO-dependent protection of witochoodria against ischemia-reperfusion. This hypothesis will be tested by pursuit of the following Specific Aims: 1) Determine the effects of NO on mitochondrial function in hearts isolated from normal mice and INOS knockout mice given oral low dose alcohol 2) Determine the effects of low dose alcohol on the changes in mitochondrial function in hearts subject to ischemia-reperfusion isolated from these animals. The information gained from the accomplishment of these specific aims will give insight into the mechanisms of alcohol in cardioprotection through NO-dependent mechanisms.